It has taken a long time for the US to confirm that Barack Obama's famous "red line" in Syria has in fact been crossed – but it is still unclear whether the use of chemical weapons by Bashar al-Assad's regime will lead to a significant shift in American and western policy.

News that the administration is to increase its "non-lethal assistance" to Syria's civilian opposition is simply more of the same in terms of what the US, UK and France have already been doing for months as Assad's forces have gained the upper hand on the ground.

If any significant change has now been authorised by Obama, it is the expansion of undefined "assistance" to the rebels' Supreme Military Council (SMC) – which has so far been the recipient of weapons paid for and delivered by Saudi Arabia, reportedly with the help of the CIA. The White House said explicitly that it had not decided on setting up a "no-fly zone" in Syrian airspace, as some have demanded.

The opaque language of Thursday's statement from the National Security Council does not spell out that the US will itself now be sending weapons, though it is hinted at by the promise to consult with Congress "in the coming weeks".

The rebels' main need is for heat-seeking anti-aircraft missiles that could rob the Syrian government of its deadly air superiority. The latest US position seems intended to dovetail with a wider western effort to at least contain Syria's crisis, which UN figures show has now claimed at least 93,000 lives. The issue will be high on the agenda of next week's G8 summit in Northern Ireland, where Obama will come face to face with Vladimir Putin, Assad's principal backer.

Talk of how the use of chemical weapons, even in limited quantities, "violates international norms and crosses clear red lines that have existed within the international community for decades" reflects the need for a wide consensus.

The hope is that the US and Russia can together wield enough influence – Washington with the fractured and squabbling Syrian opposition and Moscow with Assad – to cajole them into attending a peace conference in Geneva despite the apparently unbridgeable gap between the two sides.

In addition to the rising human cost of the war, there is mounting international alarm at the instability and violence now affecting all of Syria's neighbours. The increasingly open role of the Iranian-backed Lebanese Shia militia Hezbollah is a factor of grave concern. Its fighters helped Syrian forces win back the town of Qusair near Homs last week and they may be in action again in a looming offensive against rebel-held parts of Aleppo.

US and western policy, meanwhile, still looks as cautious and stumbling as it has been at any time since the Syrian tragedy began.

• The headline on this article was amended on 14 June 2013 to better reflect the content of the article.